1. Field of the Invention
This invention relates to a control unit for thyristors of a cycloconverter supplied by a three phase network and, in particular, to a control unit of the type in which a sawtooth voltage is generated in dependence on the zero crossing of a phase voltage and, in which, a firing command is generated for the thyristors when the sawtooth voltage agrees with a control voltage.
2. Description of the Prior Art
Control units of the aforesaid type in which integrators are employed to generate the sawtooth voltage are known, for example, from German Auslegeschrift 2,119,525. In these known arrangements, a separate integrator is provided for generating the sawtooth wave corresponding to each phase voltage and to each polarity of the half-waves of each phase voltage. In addition to requiring complex circuiting, the use of separate integrators also requires in each case an adjustment of the integrators to the same characteristic by means of potentiometers when the control is started up.
It is an object of the present invention to provide a control unit of the above type in which as few integrators as possible are required.